If you plan on keeping your site for a long time, you can turn on domain auto-renew. It makes life easier for me since its one less thing to do. I have forgotten to renew domain before and it really hurts when your site or email is down when you need it most.

Auto Renew can be found in your Member Zone under the domain section, it'll say Domain Auto Renew(OFF). Just click this and then hit TURN ON. I've found that this feature is set to renew about 5 days before your domain expires to make sure you have time if some kind of issue occurs.